1 chapter 7 chemical quantities 7.2 the mole copyright © 2005 by pearson education, inc. publishing...

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Chapter 7 Chemical Quantities

7.2

The Mole

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Collection Terms

A collection term states

a specific number of items.

• 1 dozen donuts

= 12 donuts

• 1 ream of paper

= 500 sheets

• 1 case = 24 cans


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A mole (mol) is a collection that contains:

• The same number of particles as there are carbon atoms in 12.01 g of carbon

• 6.022 x 1023 atoms of an element (Avogadro’s number).

1 Mol element Number of Atoms

1 mol C = 6.022 x 1023 C atoms

1 mol Na = 6.022 x 1023 Na atoms

1 mol Au = 6.022 x 1023 Au atoms

A Mole of Atoms

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A mole

• Of a covalent compound has Avogadro’s number of molecules

1 mol CO2 = 6.022 x 1023 CO2 molecules

1 mol H2O = 6.022 x 1023 H2O molecules

• Of an ionic compound contains Avogadro’s number of formula units

1 mol NaCl = 6.022 x 1023 NaCl formula units

1 mol K2SO4 = 6.022 x 1023 K2SO4 formula units

A Mole of a Compound

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Samples of One-Mole Quantities

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Avogadro’s number 6.022 x 1023 can be written as an

equality and two conversion factors.

Equality:

1 mol = 6.022 x 1023 particles

Conversion Factors:

6.022 x 1023 particles and 1 mol 1 mol 6.022 x 1023

particles

Avogadro’s Number

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Using Avogadro’s Number

Avogadro’s number is used to convert Moles of a substance to Particles.

How many Cu atoms are in 0.50 mol Cu?

0.50 mol Cu x 6.022 x 1023 Cu atoms 1 mol Cu

= 3.0 x 1023 Cu atoms


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Using Avogadro’s Number

Avogadro’s number is used to convert Particles of a substance to Moles.

How many moles of CO2 are in

2.50 x 1024 CO2 molecules?

2.50 x 1024 CO2 x 1 mol CO2

6.022 x 1023 CO2

= 4.15 mol CO2

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1. The number of atoms in 2.0 mol Al is

A. 2.0 Al atoms

B. 3.0 x 1023 Al atoms

C. 1.2 x 1024 Al atoms

2. The number of moles of S in 1.8 x 1024 atoms S is

A. 1.0 mol S atoms

B. 3.0 mol S atoms

C. 1.1 x 1048 mol S atoms

Learning Check

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C. 1.2 x 1024 Al atoms

2.0 mol Al x 6.022 x 1023 Al atoms1 mol Al

B. 3.0 mol S atoms

1.8 x 1024 S atoms x 1 mol S 6.022 x 1023 S atoms

Solution

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Subscripts and Moles

The subscripts in a formula state• The relationship of atoms in the formula.• The moles of each element in 1 mol of compound.

Glucose

C6H12O6

In 1 molecule: 6 atoms C 12 atoms H 6 atoms O

In 1 mol: 6 mol C 12 mol H 6 mol O

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Subscripts State Atoms and Moles

9 mol C 8 mol H 4 mol O

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Factors from Subscripts

The subscripts are used to write conversion factors for

moles of each element in 1 mol compound. For aspirin

C9H8O4, the following factors can be written:


1 mol C9H8O4 1 mol C9H8O4 1 mol C9H8O4

and

1 mol C9H8O4 1 mol C9H8O4 1 mol C9H8O4


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Learning Check

How many O atoms are in 0.150 mol aspirin C9H8O4?

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Solution

How many O atoms are in 0.150 mol aspirin C9H8O4?

0.150 mol C9H8O4 x 4 mol O x 6.022 x 1023 O atoms

1 mol C9H8O4 1 mol O

subscript Avogadro’s

factor Number

= 3.61 x 1023 O atoms

1 chapter 7 chemical quantities 7.2 the mole copyright © 2005 by pearson education, inc. publishing...

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